Frequently Asked Questions
Straightforward answers about our relationship to VideoLAN, open source licensing, display architecture, and how MacLC handles your files.
Why does HDR look washed out, grey or too dim on my Mac?
When a player lacks a proper tone-mapping path, HDR film on a normal display is clipped to flat white.
In upstream VLC 4.0, display headroom was read once from the main screen, leaving HDR brightness wrong whenever a window moved to a second display. Sub-4K HDR content was also mis-tagged with zero-nit mastering volumes, playing wide-gamut content through the wrong primaries.
MacLC re-measures headroom on every screen, window-move and display-profile change, and applies correct tagging per stream. See the six HDR defects fixed on macOS for full details.
Why is HDR video too dark in some apps and not others?
Different media players handle tone mapping differently when fitting HDR content to a screen's physical limits. When tone mapping compresses an image incorrectly, mid-tones can appear unnaturally dark.
Under the published SMPTE ST 2084 standard, HDR10 uses the Perceptual Quantizer (PQ) curve, defining absolute luminance levels up to 10,000 nits. Displays with lower peak capabilities must adapt that range through tone mapping.
MacLC re-measures headroom on every screen, window-move and display-profile change, and offers ten selectable tone-mapping algorithms in its HDR pane. Explore MacLC's four HDR modes and configurable tone mapping.
What is display headroom, and how do I know what my Mac has?
Display headroom is the ratio between the brightest highlight a panel can produce and standard SDR white. On a display without real extended dynamic range there is no spare headroom, so highlight expansion does nothing at all.
An XDR display can go five to six times brighter than SDR white. Measured on an M3 Max running macOS 26.2, MacLC recorded a headroom multiplier of 6.15×.
MacLC displays your screen's measured brightness headroom live in its HDR settings pane. Read more about how MacLC uses measured display headroom across Apple Silicon displays.
Can I turn SDR video into HDR on a Mac?
Yes, provided your Mac has a display with real extended range (XDR or an HDR external panel). MacLC lifts highlights into the headroom your panel had spare all along, while shadows and mid-tones reach your eye at exactly the brightness they always did.
It will not invent detail that was never captured, and on an SDR display it does nothing at all.
MacLC executes highlight expansion in Metal on the default AVFoundation display path, where libplacebo is unreachable on macOS. See how MacLC expands SDR video to HDR with a live interactive curve.
What does SDR → HDR actually do?
An XDR display can go five to six times brighter than SDR white. Ordinary video files carry no HDR signal at all, leaving that headroom unused during playback.
Relabelling an SDR file as HDR blows out mid-tones — under PQ encoding the same numbers mean roughly five times the brightness, so faces go white and the whole picture looks wrong. MacLC solves this with an 895-line Metal compute shader (VLCHDRExpander) that re-encodes each SDR frame into 10-bit PQ / BT.2020.
The expansion is the identity at and below a knee at half SDR white, and quadratic above it. Because the whole RGB triplet is scaled by its largest component, hue and saturation never move.
Shadows and mid-tones reach your eye at exactly the brightness they always did; only highlights lift into spare headroom. Processing costs 0.53 ms per frame at 1080p and 0.91 ms at 4K, including the synchronous wait. View our interactive expansion curve and verification benchmarks.
Why are subtitles blindingly bright over HDR video?
In upstream VLC, subtitles were untagged over HDR video, so white subtitles rendered at full HDR luminance — searingly bright over dark scenes.
MacLC fixes this by pinning subtitles to SDR and scaling them to the ITU-R BT.2408 203-nit reference white.
Subtitles remain clean and legible without overpowering dark scenes. Learn more in the six HDR defects fixed on macOS.
Does MacLC support Dolby Vision and HLG?
Yes. Both Dolby Vision and Hybrid Log-Gamma (HLG) are supported natively in MacLC.
MacLC extracts Dolby Vision metadata from the VideoToolbox bitstream with hardened parsers, including a fix for Dolby Vision being lost to a stray bit on the very first frame.
HDR10+ dynamic metadata is carried end-to-end through the filter chain. Sources already in PQ or HLG skip the SDR → HDR step entirely. Read about Dolby Vision and HDR10+ dynamic metadata handling.
What is the difference between HDR10, HDR10+, Dolby Vision and HLG?
These formats use different transfer functions and metadata approaches to deliver extended dynamic range and wide-gamut colour.
HDR10 uses the open PQ (SMPTE ST 2084) curve. HDR10+ adds dynamic metadata, which MacLC carries end-to-end through the filter chain. Dolby Vision uses dedicated metadata, which MacLC extracts from the VideoToolbox bitstream with hardened parsers.
HLG (Hybrid Log-Gamma) is a broadcast standard requiring no metadata. Across streams, MacLC forwards mastering-display (ST 2086) and content-light-level (CTA-861.3) metadata correctly.
Which Macs can decode AV1 in hardware?
Hardware AV1 decoding is available on Apple Silicon Macs with an M3 or M4 chip.
MacLC accesses hardware AV1 decoding through VideoToolbox, gated on real hardware support. It was confirmed available on M3 Max.
Where hardware decode is unavailable, MacLC falls back to software decoding using hand-written ARM64 NEON chroma conversions that replace scalar loops on the software-decode path.
Do I need an HDR display?
Not for general playback. MacLC plays both SDR and HDR files on any Mac screen.
When playing HDR files on an SDR screen, MacLC provides a real conversion with a correct fallback on older macOS, preventing HDR film on a normal display from clipping to flat white. You can inspect our verified tone-mapping algorithms in the HDR guide.
However, SDR → HDR highlight expansion requires a display with real extended range (XDR or an HDR external panel); on an SDR display it does nothing.
Is this VLC?
MacLC is a macOS-only fork of VLC 4.0 for Apple Silicon. It keeps 100% of VLC's playback capability — the same demuxers, decoders, protocol stack and engine (libvlccore), so it plays literally everything VLC plays.
What it changes is everything around that: the HDR pipeline on Apple displays, an 8-pane settings interface, and the interface itself.
Learn more about how MacLC upgrades the macOS display architecture while preserving universal codec compatibility.
Is it affiliated with VideoLAN?
No. MacLC is completely independent and is not affiliated with, endorsed by, or supported by VideoLAN.
VLC, VideoLAN, and the traffic-cone logo are registered trademarks of VideoLAN. MacLC uses none of them. It has its own name, its own original superellipse icon, and its own bundle identifier (org.maclc.MacLC).
MacLC exists because of more than two decades of foundational work by the VideoLAN community. We credit and thank VideoLAN sincerely for building and maintaining that open-source foundation.
Is MacLC safe to install?
Yes. MacLC is open-source software licensed under GPL v2+. Every line of source code, build script, and shader is publicly auditable on GitHub.
Because MacLC is an independent open-source project, our pre-release beta builds are not yet notarized by Apple. When opening the app for the first time, macOS Gatekeeper will notify you that the developer cannot be verified.
To launch the app, right-click (or Control-click) MacLC.app in Finder, select Open, and confirm the system dialog. You only need to do this once.
Does MacLC work on Intel Macs?
No. MacLC is built exclusively for Apple Silicon (M1 or newer) running macOS 13 Ventura or later.
Targeting Apple Silicon exclusively enables hand-written ARM64 NEON chroma conversions replacing scalar loops on the software-decode path and a dedicated Metal compute pipeline for HDR.
If you use an Intel Mac, official VLC builds from VideoLAN remain the right choice.
Is it really free?
Yes. MacLC is licensed under the GNU General Public License (GPL-2.0-or-later), and the underlying libVLC engine is licensed under the LGPL (LGPL-2.1-or-later).
The complete source code is always publicly available at no cost on GitHub.
There is no paid tier, no subscription, no registration, no feature gating, and nothing is held back.
Why ask for donations if it is free?
MacLC is free, but maintaining a large macOS fork requires ongoing work and real hardware expenses:
- Merging upstream VLC: Every VLC update must be pulled, built, and verified against our macOS layers.
- macOS release verification: Apple changes tone-mapping semantics between versions and the whole path has to be re-verified.
- Apple Developer program: Notarisation and code signing cost money every year, whether anyone donates or not.
- Physical test displays: HDR claims cannot be verified on a spec sheet. Verifying behaviour across displays means having the displays.
If you can donate, your contribution funds this work directly. If you cannot, you are warmly invited to use MacLC for free.
Will it break my VLC install?
No. First launch copies your preferences, application-support directory and defaults across.
It only ever copies — it never moves, modifies, or deletes your existing VLC files.
Your existing VLC installation is left exactly as it was and keeps working.
How do I go back to VLC?
Simply open your existing VLC application. Because MacLC uses its own bundle identifier (org.maclc.MacLC) and only copies settings across, your existing VLC installation was never altered.
Your existing VLC install is left exactly as it was and keeps working.
Why should I trust a fork with my media?
Because the code is open source, auditable, and grounded in transparent measurements. The playback engine is libvlccore, keeping 100% of VLC's playback capability.
MacLC resolved six confirmed defects and nine missing capabilities in upstream VLC 4.0 on Apple Silicon, eliminating use-after-free crashes on quit, teardown deadlocks, and subtitle luminance spikes.
We are equally transparent about what is not reviewed: the mathematics of the shader is verified against a CPU reference, but two things have not been visually reviewed by a human: the interface redesign, and the on-screen appearance of the SDR → HDR grade. We invite you to inspect the source and verify it yourself.
How do I report a bug?
Bug reports and regressions can be submitted on our GitHub Issues tracker.
To help us diagnose issues quickly, please include your Mac model, macOS version, display model, measured display headroom (from MacLC's HDR Settings pane), and media transfer function.